1. Field of the Invention
This invention relates to a process for the production of oxidatively crosslinkable, water-dilutable binders containing chemically incorporated carboxyl groups and olefinically unsaturated hydrocarbon radicals capable of oxidative drying, to the binders obtained by this process and to their use in coating compositions and sealing compositions.
2. Description of the Prior Art
Oxidatively drying, water-soluble binders based on alkyd resins are known (cf., for example, DE-PS 1,669,141, EP-A-0,002,488 and the literature cited therein). Coatings produced from such binders are normally distinguished by good optical and mechanical film properties. However, problems are caused by the relatively high vulnerability of such products to saponification in aqueous neutralized solution due to the basic polyester skeleton. Phase separation or rather sedimentation occurs in storage. There is a need for products having improved saponification stability and a shorter drying time.
EP-A-0,350,684 describes aqueous fatty-alcohol-modified copolymers of maleic acid anhydride as binders which are distinguished by rapid physical drying, form coatings having good optical film properties and, in addition, crosslink by oxidation. The disadvantage of these binders is that the copolymers used can only be produced using considerable quantities of inert solvents which generally remain in the water based coating compositions ultimately obtained. This runs contrary to the main purpose of water-based coating compositions, i.e., to minimize the content of volatile inert solvents.
Accordingly, an object of the present invention is to provide binders for water-based coating compositions which possess the advantages of the binders according to EP-A-0,350,684 without the disadvantage of a very high solvent content.
This object may be achieved by the process according to the invention which is described in detail hereinafter. The process according to the invention is based on the surprising discovery that when copolymerizable, but not homopolymerizable, monomers of the type described in detail hereinafter, which are liquid under the reaction conditions, are used, the use of inert solvents in the production of the copolymers can be reduced to a minimum so that the solvent content of the water-based coating compositions ultimately obtained is well below by weight.